Bob and his fish friends have been noticing these weird silver things hanging out the in the water lately. They have also noticed that some of their friends seem to be disappearing. Bob wonders if the two are related. Their school of fish started with 450 fish in it but now they only have 360 fish in their school. By what percentage was the population of their school of fish reduced?

In a test for esp (extrasensory perception), a subject is told that cards only the experimenter can see contain either a star, a circle, a wave, or a square. as the experimenter looks at each of 20 cards in turn, the subject names the shape on the card. a subject who is just guessing has probability 0.25 of guessing correctly on each card. a. the count of correct guesses in 20 cards has a binomial distribution. what are n and p? b. what is the mean number of correct guesses in 20 cards for subjects who are just guessing? c. what is the probability of exactly 5 correct guesses in 20 cards if a subject is just guessing?